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Go to the Index of 120 Philosophers Squared

René Descartes (1596-1650), French philosopher and mathematician. He was a ‘Father of Modern Philosophy’ and is famous for “I think, therefore I am.” He is a father of modern mathematics, creating the Cartesian system of measurement in multi-dimensions. He emancipated humanity from the church by granting the individual autonomous reason.

Rene Descartes

Rene Descartes, Father of modern philosophy and mathematics

Quotes attributed to Rene Descartes

“In order to improve the mind, we ought less to learn, than to contemplate.”

“Common sense is the most fairly distributed thing in the world, for each one thinks he is so well-endowed with it that even those who are hardest to satisfy in all other matters are not in the habit of desiring more of it than they already have.”

“There is nothing so strange and so unbelievable that it has not been said by one philosopher or another.”

Cogito ergo sum, “I think, therefore I am.” alt “I think therefore I exist.”

My attempt to link isolated quotes into a flowing discourse

“In philosophy, when we make use of false principles, we depart the farther from the knowledge of truth and wisdom exactly in proportion to the care with which we cultivate them, and apply ourselves to the deduction of diverse consequences from them, thinking that we are philosophizing well, while we are only departing the farther from the truth; from which it must be inferred that they who have learned the least of all that has been hitherto distinguished by the name of philosophy are the most fitted for the apprehension of truth.”

“But to live without philosophizing is in truth the same as keeping the eyes closed without attempting to open them; and the pleasure of seeing all that sight discloses is not to be compared with the satisfaction afforded by the discoveries of philosophy.”

“I have observed, on examining the natural constitutions of different minds, that there are hardly any so dull or slow of understanding as to be incapable of apprehending good opinions, or even of acquiring all the highest sciences, if they be but conducted along the right road.”

“When he has acquired some skill in discovering the truth in these questions, he should commence to apply himself in earnest to true philosophy, of which the first part is Metaphysics, containing the principles of knowledge, among which is the explication of the principal attributes of God, of the immateriality of the soul, and of all the clear and simple notions that are in us; the second is Physics, in which, after finding the true principles of material things, we examine, in general, how the whole universe has been framed.”

“Yet although the senses sometimes deceive us about objects that are very small or distant, that doesn’t apply to my belief that I am here, sitting by the fire, wearing a winter dressing-gown, holding this piece of paper in my hands, and so on. It seems to be quite impossible to doubt beliefs like these, which come from the senses.”

“At the same time I must remember that I am a man, and that consequently I am in the habit of sleeping, and in my dreams representing to myself the same things or sometimes even less probable things, than do those who are insane in their waking moments.”

“Suppose then that I am dreaming—it isn’t true that I, with my eyes open, am moving my head and stretching out my hands. Suppose, indeed that I don’t even have hands or any body at all. Still, it has to be admitted that the visions that come in sleep are like paintings: they must have been made as copies of real things; so at least these general kinds of things— eyes, head, hands and the body as a whole—must be real and not imaginary.”

“As if I didn’t remember other occasions when I have been tricked by exactly similar thoughts while asleep! As I think about this more carefully, I realize that there is never any reliable way of distinguishing being awake from being asleep. This discovery makes me feel dizzy, which itself reinforces the notion that I may be asleep!”

“To doubt such things I would have to liken myself to brain-damaged madmen who are convinced they are kings when really they are paupers, or say they are dressed in purple when they are naked, or that they are pumpkins, or made of glass. Such people are insane, and I would be thought equally mad if I modeled myself on them.”

“So I shall suppose that some malicious, powerful, cunning demon has done all he can to deceive me—rather than this being done by God, who is supremely good and the source of truth. I shall think that the sky, the air, the earth, colors, shapes, sounds and all external things are merely dreams that the demon has contrived as traps for my judgment.”

“I shall stubbornly persist in this train of thought; and even if I can’t learn any truth, I shall at least do what I can do, which is to be on my guard against accepting any falsehoods, so that the deceiver—however powerful and cunning he may be—will be unable to affect me in the slightest.”

“It might be thought that since the reality that I am considering in my ideas is merely representative, it might be possessed by its cause only representatively and not intrinsically.”

“If I had derived my existence from myself, I would not now doubt or want or lack anything at all; for I would have given myself all the perfections of which I have any idea. So I would be God.”

“The word ‘invent’ points to what is wrong with relying on my imagination in this matter: if I used imagination to show that I was something or other, that would be mere invention, mere story-telling; for imagining is simply contemplating the shape or image of a bodily thing.”

“Well, if God didn’t exist, from what would I derive my existence? It would have to come from myself, or from my parents, or from some other beings less perfect than God (a being more perfect than God, or even one as perfect, is unthinkable).”

“Being able to imagine isn’t essential to me, as being able to understand is; for even if I had no power of imagination I would still be the same individual that I am. This seems to imply that my power of imagining depends on something other than myself; and I can easily understand that · if there is such a thing as my body—that is ·, if my mind is joined to a certain body in such a way that it can contemplate that body whenever it wants to—then it might be this very body that enables me to imagine corporeal things.”

“As vividly as it teaches me anything, my own nature teaches me that I have a body, that when I feel pain there is something wrong with this body, that when I am hungry or thirsty it needs food and drink, and so on. So I shouldn’t doubt that there is some truth in this.”

“But the error of those who lean too much to the side of doubt, was not followed for any length of time, and that of the opposite party has been to some extent corrected by the doctrine that the senses are deceitful in many instances.”

“Of philosophy I will say nothing, except that when I saw that it had been cultivated for many ages by the most distinguished men, and that yet there is not a single matter within its sphere which is not still in dispute, and nothing, therefore, which is above doubt, I did not presume to anticipate that my success would be greater in it than that of others; and further, when I considered the number of conflicting opinions touching a single matter that may be upheld by learned men, while there can be but one true, I reckoned as well-nigh false all that was only probable.”


“The first [maxim] was to obey the laws and customs of my country, adhering firmly to the faith in which, by the grace of God, I had been educated from my childhood and regulating my conduct in every other matter according to the most moderate opinions, and the farthest removed from extremes, which should happen to be adopted in practice with general consent of the most judicious of those among whom I might be living.”

“My second maxim was to be as firm and resolute in my actions as I was able, and not to adhere less steadfastly to the most doubtful opinions, when once adopted, than if they had been highly certain; imitating in this the example of travelers who, when they have lost their way in a forest, ought not to wander from side to side, far less remain in one place, but proceed constantly towards the same side in as straight a line as possible, without changing their direction for slight reasons, although perhaps it might be chance alone which at first determined the selection; for in this way, if they do not exactly reach the point they desire, they will come at least in the end to some place that will probably be preferable to the middle of a forest .”

“My third maxim was to endeavor always to conquer myself rather than fortune, and change my desires rather than the order of the world, and in general, accustom myself to the persuasion that, except our own thoughts, there is nothing absolutely in our power; so that when we have done our best in things external to us, all wherein we fail of success is to be held, as regards us, absolutely impossible: and this single principle seemed to me sufficient to prevent me from desiring for the future anything which I could not obtain, and thus render me contented.”

“But the chief ground of my satisfaction with thus method, was the assurance I had of thereby exercising my reason in all matters, if not with absolute perfection, at least with the greatest attainable by me: besides, I was conscious that by its use my mind was becoming gradually habituated to clearer and more distinct conceptions of its objects; and I hoped also, from not having restricted this method to any particular matter, to apply it to the difficulties of the other sciences, with not less success than to those of algebra.”

“This method, from the time I had begun to apply it, had been to me the source of satisfaction so intense as to lead me to, believe that more perfect or more innocent could not be enjoyed in this life; and as by its means I daily discovered truths that appeared to me of some importance, and of which other men were generally ignorant, the gratification thence arising so occupied my mind that I was wholly indifferent to every other object.”

“But even superior men have no reason for any great anxiety to know these principles, for if what they desire is to be able to speak of all things, and to acquire a reputation for learning, they will gain their end more easily by remaining satisfied with the appearance of truth, which can be found without much difficulty in all sorts of matters, than by seeking the truth itself which unfolds itself but slowly and that only in some departments, while it obliges us, when we have to speak of others, freely to confess our ignorance.”


“When it is not in our power to follow what is true, we ought to follow what is most probable.”

“If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things.”

“The long chains of simple and easy reasonings by means of which geometers are accustomed to reach the conclusions of their most difficult demonstrations, had led me to imagine that all things, to the knowledge of which man is competent, are mutually connected in the same way, and that there is nothing so far removed from us as to be beyond our reach, or so hidden that we cannot discover it, provided only we abstain from accepting the false for the true, and always preserve in our thoughts the order necessary for the deduction of one truth from another.”

“A state is better governed which has few laws, and those laws strictly observed.”

Descartes said in Latin, “Cogito ergo sum,” which gives options for English restatement. Usually stated, “I think, therefore I am.” Several years ago I wrote “I think I think, therefore I think I am.” and my dog Tiger, upon farting, opined, “I stink, therefore I am”; at the moment “I know I think therefore I know I am,” and that statement seems more authoritative and convincing than merely thinking I think. It evolved into observing you, and I can say, “I think you think, but I know you are as surely as I know I think and I know I am.”

“In order to improve the mind, we ought less to learn, than to contemplate.” This is different than the motto of education of Descartes’ day, The goal of education was “To learn to listen and speak, to read and write.” Contemplating demands more, it requires internal mental work. Because of my penchant for action based on careful analysis, and the avoidance of empty learning which never has the possibility of leading to action, I had to pause on Descartes’ word contemplate. I would contend that contemplating is action, it is mental action based on what is known and what might be deduced from what is known, but I believe even this should be couched in ways that might lead to the possibility of action, even though its use may not be known or even knowable at the moment. In that way it is similar to Karl Popper’s ideas about stating scientific theories and findings in a ways that are falsifiable. I want them to be potentially useful. Or as the US Patent Law requires, “new and useful.”

“There is nothing so far removed from us as to be beyond our reach, or so hidden that we cannot discover it, provided only we abstain from accepting the false for the true.” This concept is based on having tested and proven sound ideas upon which other ideas may be safely founded. This is like a geometry of ideas based on axioms and building a logical structure for measuring and using space. That aspect of modern reality that works is based on historical reality that functioned. It is a form of societal evolution.

“Divide each difficulty into as many parts as is feasible and necessary to resolve the problem.” This concept is similar to Ockham’s Razor in intent, but different in the goal of finding a working concept. Ockham wrote, “Entities should not be multiplied beyond necessity.” Descartes alone created many profound advancements in various fields, philosophy, mathematics, geometry and religion using his methods and theories, whereas several hundred years of the entire Scholastic community produced few. The old saying, “You may know them by their fruits” applies. Thus –

Amplify the verifiable assumptions until a working solution can be demonstrated.